add filterFalsy snippet, tags, and tests

test/filterFalsy.test.js

@@ -0,0 +1,18 @@
+const expect = require('expect');
+const {filterFalsy} = require('._30s.js');
+
+test('filterFalsy is a Function', () => {
+  expect(filterFalsy).toBeInstanceOf(Function);
+});
+
+test('filterFalsy filters different types of falsy values', () => {
+  expect(filterFalsy(['', true, {}, false, 'sample', 1, 0])).toEqual([true, {}, 'sample', 1]);
+});
+
+test('filterFalsy returns an empty array if you pass it an array of falsy values', () => {
+  expect(filterFalsy(['', 0, false, '', false, 0])).toEqual([]);
+});
+
+test('filterFalsy returns all of the truthy elements in an array', () => {
+  expect(filterFalsy([true, null, 'test', {}, []])).toEqual([true, 'test', {}, []]);
+});